Somatostatin (SS) and various acylated derivatives of SS are described in U.S. Pat. No. 3,904,595 to Guillemin et al. SS is a tetradecapeptide having the following structure, with amino acid moieties numbered from left to right in accordance with usual nomenclature: ##STR2##
U.S. application, Ser. No. 675,149, filed Apr. 9, 1976, describes further SS analogs wherein substitutions for amino acid moieties in the backbone of SS provide a peptide which is therapeutically valuable when introduced, either directly or indirectly, into the bloodstream of mammals to inhibit the secretion of growth hormone from the pituitary gland and insulin and gluagon. from the pancreas. These peptides have D-Trp substituted for Trp in the eight position of SS and may have Ala substituted in the five position or simply have this position deleted.
U.S. Pat. No. 4,133,782, issued Jan. 9, 1979 to Vale et al., describes other analogs of SS which possess dissociated biological activity in respect to the inhibition of growth hormone, insulin or glucagon secretion. Examples of these peptides include des-Asn.sup.5 -[D-Trp.sup.8 ]-SS; [D-Ser.sup.13 ]-SS; [D-Trp.sup.8,D-Ser.sup.13 ]SS; [D-Cys.sup.14 ]-SS;.
U.S. Pat. No. 4,105,603, describes peptides having fewer amino acid residues than SS but which still possess biological activity in respect to the inhibition of growth hormone, insulin or glucagon secretion. A number of nonapeptides and octapeptides are illustrated, some of which have dissociated activity. The octapeptide covered by this patent having the formula: EQU H--Cys--Phe--Phe--D--Trp--Lys--Thr--Phe--Cys--OH
shows prolonged inhibitory activity on the secretion of insulin, glucogon pancreatic polypeptide and gastrin in human subjects following subcutaneous administration.